Dentists have long used small, handheld mirrors when performing dental procedures such as oral surgery and restorative dentistry. The stereotypical dental mirror has a stainless handle with a reflecting surface affixed at an angle on the end of the handle. The reflecting surface in such a mirror is usually provided by a conventional glass mirror.
Such mirrors have disadvantages. They are costly to manufacture. They have a high tendency to fog up due to the relatively large heat capacity and conductance of the glass and metal materials which results in the mirror tending to remain at room temperature and condensing moisture on its surface when a patient exhales. This type of dental mirror also requires sterilization between patients via chemical or thermal processes.
Additionally, although the material in these dental mirrors can withstand chemical and thermal sterilization, the interface between the mirror and the metal handle is susceptible to retaining germs which may occasionally survive the sterilization process. Even when sterilization of the mirror is successful, unsightly debris and grit may be trapped in the gap around the mirror, and can be difficult to remove.
For these and other reasons, disposable dental mirrors have become popular in recent years. Disposable mirrors may be discarded after use so sterilization is not needed and transmission of viable pathogens between patients is completely avoided. Since they do not need to be able to withstand sterilization procedures, they may be made with lighter weight materials resulting in less fatigue during use. Disposable mirrors are less costly, and a dentist does not have to be so concerned with avoiding small scratches or abrasions on the mirror surface since the mirror may be simply discarded if damaged. Thus, disposable mirrors may be placed more closely to the work being done and the drill or other tools which might damage the mirror, resulting in a better view.
Typically, disposable mirrors are similar in configuration to the conventional, non-disposable mirror described above, but are made with less expensive materials. Handles may be a plastic material which can be made in large quantities at low expense by injection molding or other modern manufacturing methods. The reflecting surface is most often provided by a glass mirror.
While currently available disposable mirrors are less expensive than non-disposable mirrors, reducing costs still further is an on-going challenge. For example, U.S. Pat. No. 3,829,199 shows a disposable dental mirror which has a non-disposable handle which snaps into a disposable mirror/retainer assembly, thus reducing the cost of the disposable portion.
The cost of disposable mirrors becomes an even more important factor with a new dental technique call air abrasive dentistry. In this procedure, the dental drill normally used to remove decayed tooth material is supplemented or replaced by a high velocity air stream containing particles which abrade away the decayed tooth portions. In such procedures, an inherent problem is that some of the abrasive particles will ricochet off the tooth and impact the mirror surface with sufficient velocity to etch and damage it. Mirrors used in such procedures can have a very short lifetime, depending on the location of the cavity, and can become unusable within a few seconds.
Glass dental mirror pose another dilemma. A front surface mirror is desirable in a dental mirror to reduce distortion resulting from the double reflections of a rear surface mirror and refraction as light passes through the glass layer of the mirror. Front surface glass mirrors are, however, very delicate and susceptible to scratching from even minor contact by a dental instrument or drill. As a result, dental mirrors are available in both front and rear surface types to meet these conflicting requirements. Another approach to this problem has been to make the reflecting surface from a highly polished metal surface. While this provides a front surface mirror that is more durable than a glass front surface mirror, it is more expensive to replace when the reflecting surface is inevitably damaged.